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Policies

Policies provide the ability to modify the behavior of operations.

This document provides information on the structure of policy objects for specific operations and the allowed values for some of the policies.

Objects

Policy objects are structs which define the behavior of associated operations.

When invoking an operation, you can choose:

  • pass nil as policy. A relevant Policy with default values will be generated automatically.
  • Use a generator to make the policy; e.g. NewWritePolicy(gen, ttl)
  • Generate a policy object directly; e.g.
  Policy{
    Priority:            Priority.DEFAULT,
    Timeout:             0 * time.Millisecond, // no timeout
    MaxRetries:          2,
    SleepBetweenRetries: 500 * time.Millisecond,
    SleepMultiplier:     1.5
  }

Usage Example:

  client.Get(nil, key);
  client.Get(NewPolicy(), key);

Base Policy Object

A policy effecting the behaviour of read operations.

Attributes:

  • Priority – Specifies the behavior for the key. For values, see Priority Values. * Default: Priority.DEFAULT
  • Timeout – time.Duration datatype. Maximum time to wait for the operation to complete. If 0 (zero), then the value means there will be no timeout enforced. * Default: 0 * time.Milliseconds (no timeout)
  • MaxRetries – Number of times to try on connection errors. * Default: 2
  • SleepBetweenRetries – Duration of waiting between retries. * Default: 500 * time.Milliseconds
  • SleepMultiplier - The multiplying factor to be used for exponential backoff during retries. * Default: 1.0

WritePolicy Object

A policy effecting the behaviour of write operations.

Includes All Base Policy attributes, plus:

  • RecordExistsAction – Qualify how to handle writes where the record already exists. For values, see RecordExistsAction Values. * Default: RecordExistsAction.UPDATE
  • GenerationPolicy – Qualify how to handle record writes based on record generation. For values, see GenerationPolicy Values. * Default: GenerationPolicy.NONE (generation is not used to restrict writes)
  • Generation – Expected generation. Generation is the number of times a record has been modified (including creation) on the server. If a write operation is creating a record, the expected generation would be 0 * Default: 0
  • Expiration – Record expiration. Also known as ttl (time to live). Seconds record will live before being removed by the server. For values, see Expiration Values. * Default: Expiration.TTLServerDefault

QueryPolicy Object

A policy effecting the behaviour of query operations.

Includes All Base Policy attributes, plus:

  • MaxConcurrentNodes – Maximum number of concurrent requests to server nodes at any point in time. If there are 16 nodes in the cluster and maxConcurrentNodes is 8, then queries will be made to 8 nodes in parallel. When a query completes, a new query will be issued until all 16 nodes have been queried. * Default: 0 All nodes.
  • RecordQueueSize – Number of records to place in queue before blocking. Records received from multiple server nodes will be placed in a queue. A separate goroutine consumes these records in parallel. If the queue is full, the producer goroutines will block until records are consumed. * Default: 50

ScanPolicy Object

A policy effecting the behaviour of scan operations.

Includes All Base Policy attributes, plus:

  • ScanPercent – ScanPercent determines percent of data to scan. Valid integer range is 1 to 100. * Default: 100 All records.
  • MaxConcurrentNodes – Maximum number of concurrent requests to server nodes at any point in time. If there are 16 nodes in the cluster and maxConcurrentNodes is 8, then scans will be made to 8 nodes in parallel. When a scan completes, a new scan will be issued until all 16 nodes have been queried. * Default: 0 All nodes together.
  • ConcurrentNodes – Issue scan requests in parallel or serially. * Default: true Concurrently.
  • IncludeBinData – Indicates if bin data is retrieved. If false, only record metadata are retrieved. * Default: true
  • FailOnClusterChange – Terminate scan if cluster in fluctuating state. * Default: true
  • RecordQueueSize – Number of records to place in queue before blocking. Records received from multiple server nodes will be placed in a queue. A separate goroutine consumes these records in parallel. If the queue is full, the producer goroutines will block until records are consumed. * Default: 5000

Values

The following are values allowed for various policies.

GenerationPolicy Values

NONE

Writes a record, regardless of generation.

EXPECT_GEN_EQUAL

Writes a record, ONLY if generations are equal.

EXPECT_GEN_GT

Writes a record, ONLY if local generation is greater-than remote generation.

RecordExistsAction Values

UPDATE

Create or update record.

Merge write command bins with existing bins.

UPDATE_ONLY

Update record only. Fail if record does not exist.

Merge write command bins with existing bins.

REPLACE

Create or replace record.

Delete existing bins not referenced by write command bins.

Supported by Aerospike 2 server versions >= 2.7.5 and

Aerospike 3 server versions >= 3.1.6.

REPLACE_ONLY

Replace record only. Fail if record does not exist.

Delete existing bins not referenced by write command bins.

Supported by Aerospike 2 server versions >= 2.7.5 and

Aerospike 3 server versions >= 3.1.6.

CREATE_ONLY

Create only. Fail if record exists.

Priority Values

DEFAULT

The server defines the priority.

LOW

Run the database operation in a background thread.

MEDIUM

Run the database operation at medium priority.

HIGH

Run the database operation at the highest priority.

Expiration Values

TTLServerDefault

Default to namespace configuration variable "default-ttl" on the server.

TTLDontExpire

Never expire.

Supported by Aerospike 2 server versions >= 2.7.2 and Aerospike 3+ server.

TTLDontUpdate

Do not change ttl when record is written.

Supported by Aerospike server versions >= 3.10.1.

> 0

Actual expiration in seconds.